I've played Soul Sacrifice before, but only for a short time,as it was lent to me. Now that I am able to really play freely,having bought the game, I must say this is a very addicting title!

There are a lot of comparisons to Monster Hunter, but I feel as though the comparisons should be abandoned, as this is simply a part of a genre that MH pioneered (the farming and boss hunting,mutliplayer,arena-esque,type of game) instead of being a clone or cash-in. I have played Monster Hunter quite extensively,having put hundreds of hours across the PSP's "Freedom" titles, yet I find myself more effectively drawn to this game than MH.

The reason being that

1. This game has a story, and a pretty engaging one at that.(MH doesn't have a real story,for those who haven't played the it). The story is very dark and apocalyptic (technically post-apocalyptic), with your actions for the most part having a bearing on it's nuances (though there are few choices with far-reaching implications,due to the software's limitations and the fact that Lacrima(a resource you get after every quest) can reverse alot of your choices and is highly plentiful).
2. The game is not so highly affected by your animations. One thing I disliked about MH was the fact that you had to time yourself not only in relation to your enemies attacks and defenses, but with overly exaggerated animations in mind. SS is based more upon timing in combat, not how long it takes to drink a potion or how big of an opening you leave after attacking (which is also exaggerated in MH IMO). This makes for a more action-based game,which is a definite plus.
3. You can level up. Though not every one likes to take the time to level, and sometimes grind I,and a significant portion of other players, stand as one of those who enjoys this aspect of game-play in RPGs. It just brings an extra sense of measurable progress,thereby giving more feelings of accomplishment and improvement. This also gives the player more reasons to go back to older quests and also do optional ones (the former also giving better rewards based on your performance, heightening the desire to play more)
4. That "intangible something". There is something about SS that I can't quite put my finger on, but that essence keeps me playing for hours, instead of the 30 minutes I originally set aside. The overall package is just plain fun.